This invention relates to the field of door locks, and particularly of the kind sometimes known as security locks which can only be reached for locking and unlocking from one side of the door.
Prior art devices of this kind include those disclosed in the following United States patents called to the inventor's attention during prosecution of Ser. No. 151,640:
U.S. Pat. No. 4,015,868 discloses a lock assembly having a pair of hinge plates connected by a cylindrical hinge pin. The connecting channels of the plate secured to the wall of the door jamb protrude part way into the swinging path of the door to prevent opening and closing without damage to the door.
U.S. Pat. No. 4,627,651 discloses a strike plate and face plate of a door lock in which both have apertures which come into registration when the door is closed to receive a lock bolt.
U.S. Pat. No. 2,038,462 discloses a door latch having a construction which makes it useable with either right-hand or left-hand doors.
U.S. Pat. No. 4,013,311 discloses a lock with a crossbar mounted on a door and a keeper mounted on the door frame, having a pin to extend through slots in spaced apart ears of the keeper to seat in a groove of the crossbar received between the spaced apart ears of the keeper.
Door locks of the kind known to the proir art are relatively complex or they present problems when put in use, such as the one shown in U.S. Pat. No. 4,015,868 which has connecting channels that protrude part way into the swinging path of the door to prevent opening and closing without damage to the door.
The door lock in accordance with the present invention overcomes such problems by providing a lock assembly of simplified construction, comprising two plates having interlocking channels in which the interlocking channels are constructed and positioned entirely out of the swinging path of the door.
The door lock in accordance with this invention comprises a first thin plate for securing to the jamb or upright side wall of a door frame and which is sandwiched between the outer swinging edge of the door and the door jamb when the door is closed, and a second similar thin plate for securing to the side wall of the door adjacent its outer swinging edge to align with said first plate when the door is closed.
The first thin plate has a first pair of spaced apart connecting arms extending out from the plate secured to the door jamb in the direction the door opens, the first pair of connecting arms terminating just beyond the door jamb in respective closed loops defining a first pair of axially aligned connecting channels.
The second thin plate has a second pair of spaced apart connecting arms extending out from this plate secured to the door in the direction toward the first pair of spaced apart connecting arms of the first thin plate when the door is in its closed position, the second pair of spaced apart connecting arms terminating just beyond the outer swinging edge of the door in respective closed loops defining a second pair of axially aligned connecting channels.
The uppermost connecting arms of one of the plates is received in the space between the connecting arms of the other of the connectable plates, and the lowermost connecting arm of the latter plate is received in the space between the connecting arms of the former plate, when the door is in its closed position. At such time, the connecting channels of all four connecting arms are axially aligned to provide a through channel to receive a locking pin. When the locking pin is inserted through the axially aligned connecting channels of all four of the connecting arms, the first and second plates are meshed and interlocked together to lock the door on which the second plate is secured to the door jamb on which the first plate is secured.
Each plate has three apertures to receive mounting screws therethrough to secure the first plate to the door jamb and to secure the second plate to the door.
The connecting channels of each connecting arm may all be cylindrical in cross-section to receive a locking pin of cylindrical cross-section. In the alternative, the connecting channels may be angular in cross-section to receive a locking pin of corresponding angular cross-section such as square or triangular. In a further alternative, selected ones of the connecting channels may have a cylindrical, square or other cross-section, and the locking pin may have a limited longitudinal portion of the same corresponding cross-section to pass through such selected one of the connecting channels after which the pin may be rotated out of alignment with such selected one of the connecting channels having the particularly configured cross-section. Two of the alternatively spaced apart connecting channels may have particularly configured cross-sections matching the cross-sections of two spaced apart longitudinal portions of the locking pin, whereby when the pin is positioned in only one pre-determined radial position its particularly configured cross-sections lines up with the particularly configured cross-sections of the alternatively spaced apart connecting channels so the locking pin can be inserted. The intervening connecting channels between those having the particularly configured cross-sections have an enlarged cross-section to permit rotation of the portion of the locking pin having the particularly configured cross-section when received in said intervening connecting channels. Thus, the locking pin can be rotated to rotate its particularly configured cross-sectional portions out of alignment with their respective connecting channels having the particularly configured cross-sections, thereby locking the locking pin in its interlocking position, interlocking both first and second plates together and the door to the door jamb. The locking pin cannot be removed and the door unlocked until the locking pin is rotated to the specific pre-determined radial position wherein the particularly configured cross-sectional portions of the pin and connecting channels are in alignment for withdrawal of the pin.
In another alternative, the leading insert end of the pin has a particularly configured cross-sectional configuration, such as square, and each alternative one of the inter-meshed connecting channels has a corresponding square cross-section but positioned relative to each other at different radial positions whereby the locking pin has to be rotated to one radial position to pass through a first one of such connecting channels, then being received in the enlarged cross-section of an adjacent connecting channel where it can be rotated to a second radial position for alignment with the next connecting channel having the particularly configured cross-section.
This construction protects against someone gaining entrance by breaking a hole through the door big enough to reach a hand through for withdrawal of the locking pin, or breaking the glass in doors having windows. The locking pin cannot be removed unless it is rotated into the specific pre-determined radial position, or series of different radial positions required for withdrawal.